He was Mark Kennedy, an undercover police officer working with the Metropolitan Police Force. A married man with two children, he spent 8 years living a double life — until one day his activist girlfriend of five years discovered his real passport and his cover was blown.

Kennedy's double life has become an epic disaster for the Met Police. In 2011 prosecutors were forced to abandon a case against six activists who were accused of conspiring to break into a coal-fired power station after they were asked to reveal details of their undercover agent.

Kennedy, who had since quit the police force, was suspected of having acted like an "agent provocateur", the Guardian reported. "We're not talking about someone sitting at the back of the meeting taking notes - he was in the thick of it," Danny Chivers, who was one of the six defendants in the failed case, told the BBC.

According to a 2011 interview he conducted with the Daily Mail, Kennedy's life is now ruined. He is separated from his wife and children, and has moved to the US to start again. In 2012 he claimed to have had PTSD, and said he would be suing the Met Police for failing to stop him from "falling in love".

"The police had access to all my phone calls, texts and emails, many of which were of a sexual and intimate nature," he said. "They knew where I was spending the night and with whom. They did nothing to prevent me falling in love."

Kennedy's having sexual relationships with those he was spying on has proven especially controversial. A group of 10 women and one men have accused Kennedy, another undercover officer, and the Met Police of causing emotional trauma. They argue that their basic human right to a private life was breached by the actions.

Today Justice Tugendhat ruled that the case would be heard not in public court but in a secret court usually used for cases involving the security service.

Other examples come to mind from the realms of fiction. James Bond is the most famous fictional example of a member of the intelligence services who used relationships with women to obtain information, or access to persons or property. Since he was writing a light entertainment, Ian Fleming did not dwell on the extent to which his hero used deception, still less upon the psychological harm he might have done to the women concerned. But fictional accounts (and there are others) lend credence to the view that the intelligence and police services have for many years deployed both men and women officers to form personal relationships of an intimate sexual nature (whether or not they were physical relationships) in order to obtain information or access.

The use of a fictional spy to justify the actions of a real spy has raised some eyebrows.

"In the context of the rest of the ruling," Alex Hern of the New Statesman observes, "the judge appears to be claiming that, because a famous fictional spy had fictional sexual relationships with fictional women in fiction, Parliament must have intended the Regulation of Investigatory Powers Act to bestow the ability to have deceptive sexual relationships on police spies."

Perhaps an even stranger twist in the case is the revelation that other undercover agents may have also used "personal relationships of an intimate sexual nature" as tactics. In total, 6 undercover officers have been accused of the tactic, according to the Guardian, including one police officer who is accused of having a child with a woman who presumed he was a fellow activist.